Using your All American Pressure Sterilizer

North Spore began operations in 2014 as an urban mushroom farm utilizing low-cost and easily found materials to cultivate mushrooms for local restaurants and farmer’s markets. We began with the Bucket Tek method for growing our gourmet fungi and employed cold-water pasteurization with hydrated lime to pasteurize our substrate prior to inoculation. As a reminder, pasteurization simply reduces microscopic competition in a substrate while sterilization eliminates it entirely. Our method was effective at reducing unwanted microorganisms in our containers in those early years, but did not eliminate contamination completely and would fail to meet the standards and demand of our current commercial operation. Today, several steam tanks and autoclaves give us the capacity to fully sterilize and turn out multiple kinds of substrates daily and by the hundreds, converting them into familiar products like our Spray & Grow Kits, Boomr Bags, and Organic Sterilized Grain Bags.

Refining your own technique and producing reliable sterile substrates every time you cook does not mean going out and buying an expensive autoclave, but an investment in a pressure sterilizer will absolutely step up your game. Pressure sterilizers work by increasing the temperature of steam within a sealed chamber to a given temperature (121 degrees C or 250 degrees F) and maintain that temperature for a certain amount of time (usually no less than 30 minutes). Appliances like pressure cookers, canners, and sterilizers accomplish this task and exist in various forms on the market today, but we recommend using an All American Pressure Sterilizer. Whether it be grain bags, jars, or lab equipment, All American products have proven to be the gold standard in sterilization for mushroom growers. Unlike regular pressure cookers, they feature a stopcock that prevents steam from escaping once ideal temperatures are reached and their exclusive, precision machined "metal-to-metal" sealing system prevents contaminants while positive action clamping locks align the cover to the base forming a steam-tight seal. They also feature gasket-less lids, making opening and closing easy. What’s more, because they’re crafted from the finest hand cast aluminum to resist aging and corrosion, they are truly “built to last.”

North Spore carries both stovetop and electric All American Pressure Sterilizers. The following chart is an overview of the current models available for purchase on our site.

While All American electric sterilizers operate in a stand-alone fashion, the non-electric sterilizers are best used on coil top or natural gas stoves. Specifically, models 1915X, 1925X, and 1941X are NOT recommended for use on glass top/flat ranges because their weight may cause the glass/ceramic to break. Checking with your stove’s manufacturer to confirm its cooktop surface weight limit is a good idea if you choose a non-electric sterilizer. If the units’ weight is a limiting factor, you may decide to purchase a portable camp burner or hotplate for use as a heat source instead. Keep in mind the diameter of the non-electric sterilizers is larger than most burners and may cause heat to transfer outward and damage the surrounding surface, so select a sterilizer that most closely matches the diameter of your intended burner.

1. Begin by placing the sterilizer on a flat, heat tolerant surface near an electrical outlet (electric) or place it on the heat source (non-electric).

2. Remove the cover of the sterilizer by turning the wing nuts in a counter-clockwise motion, remembering to undo two opposite wing nuts at a time.

3. Remove the inner container and inner container rack from inside the sterilizer. 

4. Apply a thin layer of lubricant, such as high vacuum grease, petroleum jelly, or olive oil to the metal to metal seal.

5. Fill the sterilizer to the water line in the bottom of the sterilizer with distilled water. The water must be directly over the heating element, NOT inside the inner container.

6. Fill the sterilizer to the water line in the bottom of the sterilizer with distilled water. The water must be directly over the heating element, NOT inside the inner container.

7. Next, place the inner container rack inside the inner container with the lip side down. While the inner container is still outside of the sterilizer, place the items to be sterilized on the inner container rack. If sterilizing lab equipment such as metal transfer tools or scalpels you may wish to place the items inside aluminum foil or autoclavable bags designed for use inside sterilizers. If sterilizing substances in closed containers without filters, such as liquid media, keep these containers slightly open to allow steam to penetrate the entire substance.

8. Arrange the items so that steam may circulate freely inside the chamber during the sterilization cycle. Check to be sure your water level inside the sterilizer is correct and then place the loaded inner container inside the sterilizer.

9. VERY IMPORTANT- Make sure that the air exhaust channel (located on the inside of the inner container) is positioned on the right side of the sterilizer. This is necessary so that when the cover is placed on the unit, you can guide the air exhaust tube into the air exhaust tube channel.

10. Place the cover on the sterilizer. Make sure the index alignment arrow on the cover aligns with the index line arrow on the side of the bottom. Also, make sure the air exhaust tube is inserted into the air exhaust tube channel.

11. Tighten the wing nuts to secure the cover in place. Always tighten two opposite wing nuts at one time to ensure the cover is on the sterilizer evenly. Never use a wrench or mechanical device to tighten the wing nuts. Plug the power supply cord into the proper outlet - 120V or 240V.

12. Next, turn the on/off toggle to the “on” position. The red pilot light should be illuminated (electric). Or turn on an outside heat source (Non-electric). Between the pilot light and the on/off toggle is the power control knob. Turn the power control to max power.

13. Open the control valve by moving the lever to the upright position. It will take approximately 45 minutes to build pressure inside the sterilizer. This may vary based on the size of the sterilizer. Steam will be drawn from the bottom of the unit up through the air exhaust tube and out of the control valve. Steam must continually escape from the control valve for at least 5 minutes.

14. Once steam has been escaping for at least 5 minutes, close the valve and let the pressure build until the gauge reads in the “green” sterilization zone.

15. Open the control valve a second time and vent the chamber an additional 3 to 5 minutes. The reason for the second venting is to avoid sterilizer failure from trapped air in the chamber, which may prevent the steam from permeating the items to be sterilized.

16. Once the chamber is properly vented, the sterilization process begins. Start timing the sterilization cycle when the gauge is in the green zone. It is recommended to run a sterilization cycle of no less than 35 minutes at a temperature of no less than 250 degrees Fahrenheit (121 degrees Celsius). Use the timer on the left side of the unit (50x and 75x only). Be sure to monitor the gauge during the sterilization cycle and adjust the power control as necessary.

17. At the end of the sterilization cycle, turn the toggle switch to “off” (electric) or outside heat source off (non-electric) and open the control valve. The valve will be very hot. To avoid potential injury, always wear heat resistant gloves to open the valve.

18. Continue monitoring the gauge until it reaches 0 PSI. Never attempt to open the sterilizer until the gauge reads zero.

19. With the pressure gauge reading zero, loosen the wing nuts. The wing nuts may be hot, so be sure to wear your heat resistant gloves when loosening them. Remove the cover. Remember to tilt the cover away from yourself to prevent injury from any remaining steam. Remove the inner container.

20. If the sterilizer is not going to be immediately used again, empty all of the water from the unit and thoroughly dry the inside of the unit. Leave the control valve open during storage to allow air to circulate through your sterilizer.

It is recommended to periodically check the metal-to-metal seal and lubricate as needed. It is very important to keep the seal lubricated because, without proper lubrication, the cover could stick and become very difficult to remove.

Be sure not to immerse your pressure gauge in water when cleaning the sterilizer. The gauge does not require any regular maintenance other than periodically checking the opening to make sure it is clear of any debris. Do not use your unit if the gauge face cracks, fills with steam or does not return to zero pressure.

It is important to periodically clean the control valve in hot, soapy water. This helps to ensure a long life and proper operation for your unit. If distilled water is not used during sterilization, calcification can build up and cause the valve to leak. To clean any built up calcification, soak the valve in vinegar and then wash in hot, soapy water and dry thoroughly.

The air exhaust tube needs to be frequently checked to ensure that air passes freely through it. It’s recommended that you blow air through the tube at least once a month to ensure that there is nothing blocking the tube. Simply remove the air exhaust tube from the control valve on the bottom of the sterilizer cover and blow through it. If you notice any difficulty cleaning the air exhaust tube of debris or notice any corrosion, it is best to discard the tube and replace it with a new one.

It is recommended that the pressure relief valve be replaced every 3 years and the overpressure plug be replaced every 6 months.

Overall, be sure to follow the manufacturer’s recommendations for use of your sterilizer for optimal performance and do not use the sterilizer for any purpose other than its intended use. Always wear heat resistant gloves when touching the sterilizer when it is in use and before it has cooled down and as in all clinical/laboratory settings, wear safety glasses when attending to your sterilizer. Never use near combustible materials. Never place items containing corrosives in the sterilizer as doing so is a fire hazard. Before each use make sure that your gauge reads zero and remember to wait for the pressure to reach zero before attempting to open the sterilizer; once the pressure is zero, the chance for steam burns is reduced.

Do not subject your sterilizer to sudden extreme temperature changes, as this may cause expansion or contraction of the metal which can damage any aluminum device. Do not move sterilizer from a cold storage area directly onto a hot flame or element. Do not add cold water to a sterilizer which has been boiled dry and remains hot. Do not cool sterilizer by pouring cold water into or on the unit. As a reminder, extreme caution must be used when moving the sterilizer especially if it contains hot liquids and never move your sterilizer while it is pressurized. Recall that the diameter of the sterilizers are often larger than most burners and may cause heat to transfer outward and damage the surrounding surface. For this reason, always use the largest burner and keep countertops clean and clear of flammable objects.

We hope that you enjoy using your new All American Pressure Sterilizer for home use in eliminating the pesky contamination we mushroom cultivators know all too well. With proper care, and whether sterilizing grain bags, mason jars or laboratory equipment, you are sure to get years out of this tried-and-true standard within the mushroom growing community. Questions or concerns? Always feel free to contact us for more information on use of your pressure sterilizer at info@northspore.com